The present invention relates in general to a fastening device for restraint belts, particularly for car safety seats for children, and more in particular to a buckle for such a fastening device.
The restraint belts used on car safety seats for children typically comprise three branches, which can be releasably connected to each other by means of a fastening device comprising a buckle attached to the free end of one of the branches and two tongue-like coupling elements (hereinafter simply referred to as “tongues”), which are attached to the other two branches and are intended to be inserted into an inner body (preferably made of metal) of the buckle along a direction of insertion and to be locked therein to ensure that the belts are fastened around the trunk of the child sitting in the seat.
More specifically, the present invention relates to a buckle provided with a snap coupling mechanism adapted to releasably couple the two tongues to the inner body, the snap coupling mechanism comprising:
a locking element supported by the inner body so as to be pivotable about an axis perpendicular to the direction of insertion between a lock position, in which it engages the tongues and thus keeps them restrained in the inner body, and an unlock position, in which it disengages the tongues thereby making them free to be ejected from or pulled out of the inner body,
a release button which is operatively connected to the locking element and can be moved by the user along a direction perpendicular both to the direction of insertion of the tongues and to the pivot axis of the locking element to cause the locking element to move from the lock position to the unlock position, thereby allowing the tongues to be ejected from the inner body, and
a pair of sliders or ejectors mounted in the inner body so as to be movable along respective directions parallel to the direction of insertion of the tongues, the sliders being urged by respective springs in order to apply on the tongues a resilient force tending to oppose the insertion of the tongues into the inner body and to make the ejection of the tongues from the inner body, when the locking element is in the unlock position, easier. In a buckle of the above-specified kind, the release button is normally kept by a spring in a raised rest position, i.e. in a rest position facing outwardly of the buckle. In order to uncouple the tongues from the buckle, the user must press the release button against the resilient force applied by the associated spring. Once released, the release button gets back into its rest position under the action of the associated spring. When the tongues are inserted into the inner body to fasten the restraint belts, the release button remains in the rest position under the action of the associated spring, independently of the tongues having been correctly inserted into the inner body and engaged by the locking element. This is particularly critical for buckles to be sold on the US market, since the regulations currently in force in the United States provide for the possibility to insert one tongue at a time into the buckle. It may therefore happen that a first tongue is correctly inserted into and coupled to the buckle and that the second tongue is inserted into the buckle but is not correctly locked by the locking element without this being immediately and unambiguously realized by the user.